1. Field of the Invention
The present invention relates to so-called stainproofing paint to prevent the deposition in sea water of marine organisms, such as shells and algae.
2. Description of the Related Art
It is very important to prevent the deposition of marine organisms to the bottoms of vessels or construction structure in sea water or the like, in view of efficient operation and maintenance thereof. As a preventive measure, paints containing organic tin have conventionally been used effectively. However, the accumulation of organic tin compounds mainly in fish has been drawing concern. From the viewpoint of public health, the use of such compounds as a stainproofing agent is likely to become more difficult. Instead of these organic tin paints, attention has been refocused again on the use of inorganic copper compounds, in particular cuprous oxide, which do not accumulate in fish and has been practically used conventionally.
As has been well known for some time, it is difficult for paints containing one of the typical inorganic copper compounds, namely, cuprous oxide, as the stainproofing agent, to have a so-called "eel paint"-like function, where a polymer such as triphenyltin methacrylate leaches out gradually from the surface.
Paints containing cuprous oxide as the stainproofing agent and rosin as the vehicle are severely damaged in marine water so they cannot function as paints with prolonged stainproofing action. It is also said that stainproofing paints using a chloride-rubber vehicle lose their stainproofing action if the cuprous oxide distributed on the surface is solubilized.
It has been shown that, in order for a coating containing cuprous oxide to exhibit stainproofing action, cuprous oxide should solubilize at 8-11 .mu.g/cm.sup.2 /day. Therefore, for a stainproofing paint to function in a stable manner, this level must be maintained constant for a prolonged period of time.
Thus, a great deal of research has been directed toward obtaining a vehicle for paints, which contains the necessary amount of cuprous oxide and in which the coating film is consistently renewed so that a sufficient amount of cuprous oxide can be supplied.
Such vehicles include a monomer forming aqueous polymer, illustrated by one example wherein vinylpyrrolidone is used as one component of a copolymer or by another example employing a monomer having a tertiary amino group.
However, stainproofing paints employing these known polymers as vehicles do not show the variation of the physical properties depending on the circumstances at use; in other words, the solubility of the polymers does not change over time.
A disposition such as observed in the "eel paint" is preferable; that is, a polymer containing cuprous oxide is renewed on the surface so as to consistently supply a constant amount of cuprous oxide.
The present inventors, as a result of pursuing their investigation of vehicles capable of releasing a sufficient amount of copper ion to exhibit stainproofing action for a prolonged period of time, using inorganic copper compounds such as cuprous oxide as a stainproofing agent, have found that this objective can be achieved by using a polymer having an acetoacetyl group as at least one component, to achieve the present invention.